|Fig. 1: Phosphate Fertilizer. (Source: Wikimedia Commons)|
Studies have shown that cigarettes and tobacco kill more Americans each year than alcohol, car accidents, homicide and suicide combined, and is currently the leading cause of preventable disease and death in the United States.  Although the percentage of smoking has decreased overtime, smoking has resulted in billions of dollars in direct medical care for adults and lost productivity.  Cigarette smoke and tobacco contain many toxic substances unnatural to put in your body, such as nicotine, tar, carbon monoxide, and arsenic.  Although nicotine and its addictive nature are the most commonly-known danger of cigarettes, there is also the danger of the radioactive isotopes Po-210 and Pb-210, which become harmful to humans when ingested. 
Tobacco products, like cigarettes, contain small amounts of radionuclides, which is one of the many reasons to stay away from the substance.  Although we are aware that tobacco smoke are the main harms of cigarettes that is significant in the development of lung cancer, radiation also plays a role. These radioactive materials found in cigarettes have been argued to have been involved in the origin of lung cancer.  Studies reveal that Po-210, Pb-210, and small quantities of Ra-226 are present in tobacco.  Additionally, studies reveal that values for Po-210 in inhaled smoking ranged from 11% to 35.7% in the total cigarette. Studies reveal that the level of polonium-210 is higher in four/five organs tested from smokers than nonsmokers.  For lungs, smokers were found to have 3.16 times more Po-210 (measured in picocuries per gram) than non smokers.  Absorbed doses of radiation is measured using units called, rads (1 gray = 1 Joule/kilogram = 100 rad). If a smoker averages two packs a day for 25 years, they would absorb about 75 rads of polonium.  The lung tissues of smokers who have died of lung cancer have absorbed about 80-100 rads of radiation.  Po-210 emits α-radiation, which luckily has a deconstructive property; human skin is enough to stop it. However, the case is a bit different for those who inhale this substance. Studies have detected Po-210 in the airways of smokers, usually concentrated in hot spots.  For chronic smokers, this chemical remains there because chemicals in cigarette smoke damages the body's cleaning systems, which would normally get rid of this built up gunk in the airways.  As a result, polonium builds up leading to greater and longer exposures to radiation.  These radioactive materials get into tobacco because some tobacco plants are grown using phosphate fertilizers; the plant then absorbs this radioactivity (see Fig. 1).  Tobacco plants also absorb small dust particles that have small amounts of radioactive materials, including polonium. 
Po-210, is one of the 25 radioactive isotopes of polonium. The element is found in the earth's crust and in small amounts in the human body. When radioactive, it releases energy in the form of radiation; however, the particles decays quickly with a relatively short half-life. At its natural state and at room temperature, it is a silver-colored metal found in uranium ores. Half of its radioactivity dies away in 140 days, its physical half-life, into stable Pb-206 by α-particle emission (an α particle has has two protons and two neutrons). Polonium-210 is used mainly in static eliminators, devices designed to eliminate static electricity in machinery.  Because it is an α omitter, Po-210 is not a concern when exposed externally. However, this substance is not one humans should be inhaling in large amounts. 
If large quantities are inhaled or consumed in a short period of time, the effects of Po-210 are usually extremely damaging and fatal.  However, for smokers who are exposed to small amounts of the chemical over an extended period of time, there is usually a long-term risk of cancer.  These radioactive substances can get trapped, causing direct and immediate damage to cells and tissues. When inhaled, the chemical becomes concentrated in red blood cells, destroying DNA taking electrons from any molecule.  Damage to DNA from polonium radiation can cause damage to different organs and tissues.  Scientists do realize that this radioactive impurity is not the only contribution of cancer for smokers; there are other substances in cigarettes that cause result in health risks, like the 70 other cancer-causing chemicals found in tobacco smoke. Additionally, like other forms of tobacco, smokeless tobacco also contain radioactive substances.  When discussing the harmful effects of cigarettes, α-radiation is just one of the many detrimental effects that is extremely underestimated, and deserves more policy progression to act on limiting radioactivity in these products.
© Melissa Lord. The author warrants that the work is the author's own and that Stanford University provided no input other than typesetting and referencing guidelines. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.
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